BIODRILL S合成基钻井液在垦利区块首次应用

First Application of the Synthetic-Based Drilling Fluid BIODRILL S in Block Kenli of Bohai Oilfield

渤海油田垦利9-1区块地层岩性复杂,且存在断层带,钻井过程中易发生泥岩水化分散和砂岩层井眼缩径等问题,井壁垮塌风险极大。针对该区块地层岩性特点和技术难题并结合环保要求,制备了一种复合型封堵材料PFMOSHIELD,构建了BIODRILL S合成基钻井液体系。该体系流变性能良好,抗钙、抗岩屑污染达26%和15%,封堵性、沉降稳定性、润滑性优异,高温高压砂盘滤失量3.2 mL,静置7 d沉降因子为0.53,极压润滑系数0.082。BIODRILL S首次在渤海湾垦利9-1区块进行了现场应用,结果表明:该体系解决了垦利9-1区块泥页岩水化和砂岩层井眼缩径问题,垦利9-1北-3定向探井三开井段上部地层钻屑完整,钻屑达4~7 cm;井眼清洁性能良好,钻井液动塑比超过0.59 Pa/mPa·s,φ6和φ3读数均超过9,剪切稀释性强,提高了井眼净化效率,有效避免形成“岩屑床”;润滑性能优异,在大井斜段(55°、70°、67°)可实现直接起钻。

Drilling operation in the Block Kenli 9-1 of the Bohai Oilfield has long been faced with high risks of borehole wall collapse resulted from complex formation lithologies,fault zones,shales that are easy to hydrate and disperse,as well as sandstones in which tight hole problem is frequently encountered.To deal with the borehole wall collapse problem a BIODRILL S synthetic based drilling fluid has been formulated.The BIODRILL S synthetic based drilling fluid is formulated with a base oil which is synthetic oil of choice,a composite plugging additive PF-MOSHIELD,as well as other drilling fluid additives,taking into account the formation lithology and environmental protection requirement.The BIODRILL S drilling fluid has good rheology,and is resistant to 26%calcium contamination and 15%cuttings contamination.Furthermore,it has excellent plugging capacity,settling stability and lubricity.The HTHP filter loss tested on a sand plate tester is 3.2 mL.The sag index of the mud after standing for 7 d is 0.53,and the extreme coefficient of friction is 0.082.BIODRILL S was first used in the Block Kenli 9-1.The application showed that:(1)the BIODRILLS can be used to solve the shale hydration problem and the tight hole problem in the sandstone formation encountered previously in this block;the drilled cuttings produced in drilling the formations in and above the third section are intact,with sizes distributed between 4 cm and 7 cm.(2)Hole cleaning is well done with the BIODRILL S drilling fluid,the ratio of YP/PV is greater than 0.59 Pa/mPa∙s,theφ6 and theφ3 reading are all greater than 9,and the drilling fluid has good shear thinning property.All these properties result in good hole cleaning and the prevention of the occurrence of cuttings bed.(3)The drilling fluid has excellent lubricity,making possible the direct tripping(out of hole)through the high angle(55°,70°and 67°)well sections.